In 1997, Masao was a passionate member of Friend's cult since its early days. He was first shown dancing in his underpants, performing his "morning healing aerobics" while listening to Friend's "healing CD"; his room was also seen with various Friend posters, and he owns Friend t-shirts. Later on, he "purified" Pierre Ichimonji, a leader of a rival cult, once again showing his fanaticism and obsession towards Friend.

Spoiler

It is discovered later that Masao was an alumni of Musashiyama Technical School, the institution Donkey teached at. He was also shown to be an accomplice in Donkey's murder.

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In 2014, Masao was incarcerated for an unknown reason in Umihotaru Prison, the same place that held Otcho, under the registration number "13". He acted as a preacher in the prison. Later he was released and became Friend's top hitman.